QI usually get penicillin for a strep throat, but my...

QI usually get penicillin for a strep throat, but my doctor recently gave me something called cephalexin. Is it a new wonder drug?

AFor the past four decades, doctors have treated strep throat with penicillin. But recent reports indicate that as many as 10 percent of all cases may not be cured by penicillin.

Any persistent sore throat should be evaluated by a physician. The soreness could be caused by a germ called beta strep, group A, that can damage your heart by causing rheumatic fever or damage your kidneys by causing nephritis. It also can cause toxic shock and scarlet fever.

Doctors often evaluate and treat sore throats by taking a throat culture and prescribing penicillin for 10 days. In the 1940s, this treatment cured almost all sore throats caused by beta strep. However, in the 1960s, failure rates as high as 10 percent were reported. In 1992, doctors were reporting failure rates as high as 30 percent.

The failure of penicillin to cure strep throat infections may be because patients stopped their medication too soon, the strep was protected by other germs that can inactivate the penicillin or increased resistance by strep against penicillin.

Doctors still prescribe penicillin for most sore throats. But if your throat still is sore three days after you start taking the penicillin, you should check with your doctor. If your throat culture grows a beta strep, you should change to a type of medication called cephalosporine. The least expensive generic form is cephalexin.

If your throat culture does not grow a beta strep, you may need blood tests to see if you are infected with mononucleosis or some other virus.